//! 数据迁移管理模块
//! 
//! 实现Redis集群的在线数据迁移功能，包括：
//! - 槽位数据迁移协调
//! - DUMP/RESTORE命令实现
//! - 迁移进度跟踪
//! - 迁移失败回滚

use crate::cluster::traits::{
    DataMigrator, MigrationTask as MigrationTaskTrait, MigrationStatus as MigrationStatusTrait, MigrationStats
};
use crate::cluster::{ClusterError, ClusterResult};
use async_trait::async_trait;
use serde::{Deserialize, Serialize};
use std::collections::HashMap;
use std::sync::Arc;
use std::time::{Duration, Instant};
use tokio::sync::{RwLock, mpsc};
use tokio::time::interval;
use tracing::{debug, info};
use uuid::Uuid;

/// 迁移状态
#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
pub enum MigrationStatus {
    /// 准备中
    Preparing,
    /// 迁移中
    InProgress,
    /// 暂停
    Paused,
    /// 完成
    Completed,
    /// 失败
    Failed,
    /// 已取消
    Cancelled,
}

impl From<MigrationStatus> for MigrationStatusTrait {
    fn from(status: MigrationStatus) -> Self {
        match status {
            MigrationStatus::Preparing => MigrationStatusTrait::Pending,
            MigrationStatus::InProgress => MigrationStatusTrait::InProgress,
            MigrationStatus::Completed => MigrationStatusTrait::Completed,
            MigrationStatus::Failed => MigrationStatusTrait::Failed,
            MigrationStatus::Cancelled => MigrationStatusTrait::Cancelled,
            MigrationStatus::Paused => MigrationStatusTrait::Pending, // 映射为Pending
        }
    }
}

/// 迁移任务
#[derive(Debug, Clone)]
pub struct ClusterMigrationTask {
    /// 任务ID
    task_id: String,
    /// 源节点ID
    source_node: String,
    /// 目标节点ID
    target_node: String,
    /// 迁移的槽位
    slots: Vec<u16>,
    /// 当前状态
    status: MigrationStatus,
    /// 创建时间
    created_at: Instant,
    /// 开始时间
    started_at: Option<Instant>,
    /// 完成时间
    completed_at: Option<Instant>,
    /// 总键数量
    total_keys: usize,
    /// 已迁移键数量
    migrated_keys: usize,
}

impl MigrationTaskTrait for ClusterMigrationTask {
    fn task_id(&self) -> &str {
        &self.task_id
    }
    
    fn source_node(&self) -> &str {
        &self.source_node
    }
    
    fn target_node(&self) -> &str {
        &self.target_node
    }
    
    fn slots(&self) -> &[u16] {
        &self.slots
    }
    
    fn status(&self) -> &MigrationStatusTrait {
        // 这里需要临时转换，实际实现中可能需要调整数据结构
        &MigrationStatusTrait::Pending // TODO: 正确转换状态
    }
    
    fn progress_percent(&self) -> f64 {
        if self.total_keys == 0 {
            0.0
        } else {
            (self.migrated_keys as f64 / self.total_keys as f64) * 100.0
        }
    }
    
    fn created_at(&self) -> Instant {
        self.created_at
    }
}

/// 迁移配置
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct MigrationConfig {
    /// 批处理大小
    pub batch_size: usize,
    /// 迁移超时时间
    pub timeout: Duration,
    /// 重试次数
    pub max_retries: u32,
    /// 重试间隔
    pub retry_interval: Duration,
    /// 并发度
    pub concurrency: usize,
}

impl Default for MigrationConfig {
    fn default() -> Self {
        Self {
            batch_size: 100,
            timeout: Duration::from_secs(60),
            max_retries: 3,
            retry_interval: Duration::from_secs(1),
            concurrency: 1,
        }
    }
}

/// 迁移进度信息
#[derive(Debug, Clone)]
pub struct MigrationProgress {
    /// 任务ID
    pub task_id: String,
    /// 进度百分比 (0-100)
    pub progress_percent: f64,
    /// 迁移速度 (keys/sec)
    pub migration_rate: f64,
    /// 预计剩余时间
    pub estimated_remaining: Option<Duration>,
    /// 最后更新时间
    pub last_update: Instant,
}

/// 迁移事件
#[derive(Debug, Clone)]
pub enum MigrationEvent {
    /// 任务开始
    TaskStarted { task_id: String, slots: Vec<u16> },
    /// 进度更新
    ProgressUpdate { task_id: String, progress: MigrationProgress },
    /// 任务完成
    TaskCompleted { task_id: String, slots: Vec<u16>, duration: Duration },
    /// 任务失败
    TaskFailed { task_id: String, slots: Vec<u16>, error: String },
    /// 任务取消
    TaskCancelled { task_id: String, slots: Vec<u16> },
}

/// 迁移统计信息
#[derive(Debug, Clone, Default)]
pub struct ClusterMigrationStats {
    pub active_migrations: usize,
    pub completed_migrations: u64,
    pub failed_migrations: u64,
    pub total_data_migrated: u64,
    pub average_migration_time: Duration,
}

impl From<ClusterMigrationStats> for MigrationStats {
    fn from(stats: ClusterMigrationStats) -> Self {
        MigrationStats {
            active_migrations: stats.active_migrations,
            completed_migrations: stats.completed_migrations,
            failed_migrations: stats.failed_migrations,
            total_data_migrated: stats.total_data_migrated,
            average_migration_time: stats.average_migration_time,
        }
    }
}

/// 数据迁移管理器
pub struct ClusterDataMigrator {
    /// 节点ID
    node_id: String,
    /// 活跃的迁移任务
    active_tasks: Arc<RwLock<HashMap<String, ClusterMigrationTask>>>,
    /// 历史任务 (最近1000个)
    history_tasks: Arc<RwLock<Vec<ClusterMigrationTask>>>,
    /// 事件发送器
    event_sender: mpsc::UnboundedSender<MigrationEvent>,
    /// 事件接收器
    event_receiver: Arc<RwLock<Option<mpsc::UnboundedReceiver<MigrationEvent>>>>,
    /// 运行状态
    is_running: Arc<RwLock<bool>>,
    /// 统计信息
    stats: Arc<RwLock<ClusterMigrationStats>>,
}

impl ClusterDataMigrator {
    /// 创建新的迁移管理器
    pub fn new(node_id: String, _config: Option<MigrationConfig>) -> Self {
        let (event_sender, event_receiver) = mpsc::unbounded_channel();
        
        Self {
            node_id,
            active_tasks: Arc::new(RwLock::new(HashMap::new())),
            history_tasks: Arc::new(RwLock::new(Vec::new())),
            event_sender,
            event_receiver: Arc::new(RwLock::new(Some(event_receiver))),
            is_running: Arc::new(RwLock::new(false)),
            stats: Arc::new(RwLock::new(ClusterMigrationStats::default())),
        }
    }
    
    /// 获取事件接收器
    pub async fn take_event_receiver(&self) -> Option<mpsc::UnboundedReceiver<MigrationEvent>> {
        self.event_receiver.write().await.take()
    }
    

}

#[async_trait]
impl DataMigrator for ClusterDataMigrator {
    type MigrationTask = ClusterMigrationTask;
    
    async fn start(&mut self) -> ClusterResult<()> {
        let mut running = self.is_running.write().await;
        if *running {
            return Ok(());
        }
        *running = true;
        
        info!("启动数据迁移管理器: {}", self.node_id);
        
        // 启动迁移监控任务
        let active_tasks = self.active_tasks.clone();
        let stats = self.stats.clone();
        let is_running_clone = self.is_running.clone();
        
        tokio::spawn(async move {
            let mut interval = interval(Duration::from_secs(10));
            
            while *is_running_clone.read().await {
                interval.tick().await;
                
                // 更新活跃任务统计
                let tasks = active_tasks.read().await;
                let mut stats = stats.write().await;
                stats.active_migrations = tasks.len();
                
                debug!("迁移任务监控: 活跃任务数 {}", tasks.len());
            }
        });
        
        Ok(())
    }
    
    async fn stop(&mut self) -> ClusterResult<()> {
        let mut running = self.is_running.write().await;
        *running = false;
        info!("数据迁移管理器已停止: {}", self.node_id);
        Ok(())
    }
    
    async fn create_migration_task(
        &mut self,
        source_node: String,
        target_node: String,
        slots: Vec<u16>,
    ) -> ClusterResult<String> {
        let task_id = Uuid::new_v4().to_string();
        
        let task = ClusterMigrationTask {
            task_id: task_id.clone(),
            source_node: source_node.clone(),
            target_node: target_node.clone(),
            slots: slots.clone(),
            status: MigrationStatus::Preparing,
            created_at: Instant::now(),
            started_at: None,
            completed_at: None,
            total_keys: 0,
            migrated_keys: 0,
        };
        
        let mut tasks = self.active_tasks.write().await;
        tasks.insert(task_id.clone(), task);
        
        // 更新统计
        let mut stats = self.stats.write().await;
        stats.active_migrations = tasks.len();
        
        info!("创建迁移任务: {} (槽位 {:?} 从 {} 到 {})", task_id, slots, source_node, target_node);
        
        Ok(task_id)
    }
    
    async fn start_migration_task(&mut self, task_id: &str) -> ClusterResult<()> {
        let mut tasks = self.active_tasks.write().await;
        if let Some(task) = tasks.get_mut(task_id) {
            if task.status == MigrationStatus::Preparing {
                task.status = MigrationStatus::InProgress;
                task.started_at = Some(Instant::now());
                
                info!("开始迁移任务: {} (槽位 {:?})", task_id, task.slots);
                
                // 发送任务开始事件
                let _ = self.event_sender.send(MigrationEvent::TaskStarted {
                    task_id: task_id.to_string(),
                    slots: task.slots.clone(),
                });
                
                // TODO: 实现实际的迁移逻辑
                // 这里应该启动异步任务来执行实际的数据迁移
                
                Ok(())
            } else {
                Err(ClusterError::Config(format!("任务 {task_id} 不在准备状态")))
            }
        } else {
            Err(ClusterError::Config(format!("任务 {task_id} 不存在")))
        }
    }
    
    async fn cancel_migration_task(&mut self, task_id: &str) -> ClusterResult<()> {
        let mut tasks = self.active_tasks.write().await;
        if let Some(mut task) = tasks.remove(task_id) {
            task.status = MigrationStatus::Cancelled;
            task.completed_at = Some(Instant::now());
            
            info!("取消迁移任务: {} (槽位 {:?})", task_id, task.slots);
            
            // 发送取消事件
            let _ = self.event_sender.send(MigrationEvent::TaskCancelled {
                task_id: task_id.to_string(),
                slots: task.slots.clone(),
            });
            
            // 移动到历史记录
            let mut history = self.history_tasks.write().await;
            history.push(task);
            
            // 更新统计
            let mut stats = self.stats.write().await;
            stats.active_migrations = tasks.len();
            
            Ok(())
        } else {
            Err(ClusterError::Config(format!("任务 {task_id} 不存在")))
        }
    }
    
    async fn get_migration_status(&self, task_id: &str) -> Option<MigrationStatusTrait> {
        if let Some(task) = self.active_tasks.read().await.get(task_id) {
            Some(task.status.clone().into())
        } else {
            // 检查历史任务
            self.history_tasks.read().await
                .iter()
                .find(|t| t.task_id == task_id)
                .map(|t| t.status.clone().into())
        }
    }
    
    async fn get_all_migration_tasks(&self) -> Vec<Self::MigrationTask> {
        let mut all_tasks = Vec::new();
        
        // 添加活跃任务
        for task in self.active_tasks.read().await.values() {
            all_tasks.push(task.clone());
        }
        
        // 添加历史任务
        for task in self.history_tasks.read().await.iter() {
            all_tasks.push(task.clone());
        }
        
        all_tasks
    }
    
    async fn get_migration_stats(&self) -> MigrationStats {
        let stats = self.stats.read().await;
        stats.clone().into()
    }
}

